In some multiphoton curing processes, such as the one described in U.S. Pat. No. 6,855,478, which is incorporated herein by reference in its entirety, a layer of material including a multiphoton curable photoreactive composition is applied on a substrate (e.g., a silicon wafer) and selectively cured using a focused source of radiant energy, such as a laser beam. A multiphoton curing technique may be useful for fabricating two-dimensional and/or three-dimensional (3D) microstructures and nanostructures.
In one fabrication technique, a voxel is created when a pulsed laser beam of near-infrared (NIR) radiation is focused into an engineered photopolymer resin. A non-linear interaction process within the resin converts a portion of the NIR radiation to a shorter wavelength, which cures the resin near a focus of the laser beam, where two photons of the NIR radiation are absorbed substantially simultaneously. The curing of the resin may be referred to as “photopolymerization,” and the process may be referred to as a “two-photon photopolymerization” process. Photopolymerization of the resin does not occur in regions of the resin exposed to portions of the NIR radiation having an insufficient intensity because the resin does not absorb the NIR radiation in those regions.
A 3D structure may be constructed voxel-by-voxel with a multiphoton photopolymerization process by controlling a location of the focus of the laser beam in three dimensions (i.e., x-axis, y-axis, and z-axis directions) relative to the resin.